Polymer compositions suitable for intraocular lenses and related methods

ABSTRACT

A polymeric material with a molecular response time that makes it suitable for use near fragile body tissues. The polymeric material is useful for both low modulus and high modulus applications thereby simplifying the multi-part polymeric article manufacturing process and creating better integrated multi-part polymeric articles. Cross-linked polymers with different moduli may be obtained utilizing the same or similar starting materials but modifying the amount of catalyst, the amount of cross-linking agent, and/or the amount of methyl vinyl cyclics.

The application is a division of application Ser. No. 11/864,450, filed28 Sep. 2007 under the same title, which is incorporated herein byreference in its entirety. Full Paris Convention priority is herebyexpressly reserved.

FIELD OF THE INVENTION

Polymeric materials, devices, and methods in which the mechanicalproperty of a polymer, such as the modulus, is selectable by alteringthe amount of catalyst used to prepare the polymer and/or by alteringthe amount of cross-linking agent or methyl vinyl cyclics is describedherein.

BACKGROUND OF THE INVENTION

The human eye is a highly evolved and complex sensory organ. It iscomposed of a cornea, or clear outer tissue which refracts light rays enroute to the pupil, an iris which controls the size of the pupil thusregulating the amount of light entering the eye, and a lens whichfocuses the incoming light through the vitreous fluid in the eye to theretina. The retina converts the incoming light to electrical energy thatis transmitted through the brain to the occipital cortex resulting in avisual image. In a perfect eye, the light path from the cornea, throughthe lens and vitreous fluid to the retina is unobstructed. Anyobstruction or loss of clarity within these structures, however, causesscattering or absorption of light rays resulting in diminished visualacuity. For example, the cornea can become damaged resulting in edema,scarring or abrasions, the lens is susceptible to oxidative damage,trauma and infection, and the vitreous fluid can become cloudy due tohemorrhage or inflammation.

As the body ages, the effects of oxidative damage caused byenvironmental exposure and endogenous free radical production accumulateresulting in a loss of lens flexibility and an accumulation of denaturedproteins that slowly coagulate, reducing lens transparency. The naturalflexibility of the lens is essential for focusing light onto the retinaby a process referred to as accommodation. Accommodation allows the eyeto automatically adjust the field of vision for objects at differentdistances. A common condition known as presbyopia results when thecumulative effects of oxidative damage diminish this flexibilityreducing near vision acuity. Presbyopia usually begins to occur inadults during their mid-forties; mild forms are treated with glasses orcontact lenses.

Lenticular cataracts are a lens disorder resulting from proteincoagulation and calcification. There are four common types of cataracts:senile cataracts associated with aging and oxidative stress; traumaticcataracts which develop after a foreign body enters the lens capsule orfollowing intense exposure to ionizing radiation or infrared rays;cataracts which are secondary to diseases such as diabetes mellitus oreye disorders such as detached retinas, glaucoma and retinitispigmentosa; and cataracts resulting from medicinal or chemical toxicity.Regardless of the cause, the disease results in impaired vision and canlead to blindness.

Treatment of severe lens disease requires the lens' surgical removal orphacoemulsification followed by irrigation and aspiration. However,without a lens, the eye is unable to focus incoming light on the retina.Consequently, artificial lenses must be used to restore vision. Threetypes of prosthetic lenses are available: cataract glasses, externalcontact lenses and intraocular lenses (IOLs). Cataract glasses havethick lenses, are uncomfortably heavy and cause vision artifacts such ascentral image magnification and side vision distortion. Contact lensesresolve many of the problems associated with cataract glasses, butrequire frequent cleaning, are difficult to handle (especially forelderly patients with symptoms of arthritis), and are not suited forpersons who have restricted tear production. Intraocular lenses are usedin the majority of cases to overcome the aforementioned difficultiesassociated with cataract glasses and contact lenses.

There are four primary IOL categories: non-deformable, foldable,expansible hydrogels and injectable. Early non-deformable IOL implantswere rigid structures composed of acrylates and methacrylates requiringa large incision in the capsular sac and were not accommodative. Thislarge incision resulted in protracted recovery time and considerablediscomfort for the patient. In an effort to reduce recovery time andpatient discomfort, numerous small incision techniques and IOLs havebeen developed.

Subsequently, IOLs were designed for smaller incision implantationthrough the use of elastomeric compositions that could be rolled orfolded, inserted into the capsular sac and then unfolded once inside.Occasionally, the fold of the IOL before insertion resulted in permanentdeformation, which adversely affected the implant's optical qualities.Further, while foldable IOLs eliminated the need for the large incision,foldable IOLs were not without drawbacks. In particular, bothnon-deformable and foldable IOLs are susceptible to mechanicaldislocation resulting in damage to the corneal endothelium.

Another approach to small incision IOL implantation uses an elastomericpolymer that becomes pliable when heated to body temperature or slightlyabove. Specifically, the IOL is made pliable and is deformed along atleast one axis, reducing its size for subsequent insertion through asmall incision. The IOL is then cooled to retain the modified shape. Thecooled IOL is inserted into the capsular sac and the natural bodytemperature warms the IOL at which point it returns to its originalshape. The primary drawback to this type of thermoplastic IOL is thelimited number of polymers that meet the exacting needs of thisapproach. Most polymers are composed of polymethylacyrlate which havesolid-elastomeric transition temperatures above 100° C. Modifications ofthe polymer substrate require the use of plasticizers that mayeventually leach into the eye causing harmful effects.

Dehydrated hydrogels have also been used with small incision techniques.Hydrogel IOLs are dehydrated before insertion and naturally rehydratedonce inside the capsular sac. However, once fully rehydrated the polymerstructure is notoriously weak due to the large amount of water absorbed.The typical dehydrated hydrogel's diameter will expand from 3 mm to 6 mmresulting in an IOL that is 85% water. At this water concentration therefractive index (RI) drops to about 1.36, which is unacceptable for anIOL since lower RI materials require the optic to be thicker to achievea given optical power.

Modern acrylate IOLs generally possess excellent mechanical propertiessuch as foldability, tear resistance and physical strength. AcrylateIOLs also are known to possess good optical properties (transparency,high refractive index, etc.) and biocompatibility. While pure acrylicIOLs have desirable mechanical, optical and biological properties, theymay have unacceptable molecular response times such that the folded orcompacted IOL may not unfold as quickly as desired. A pure acrylate IOLfabricated to have a relatively fast molecular response time may beextremely tacky and lack the desired mechanical strength. In this case,the resulting IOL may tear and/or the resulting self-tack can unfoldingdifficult.

Pure silicone IOLs generally possess excellent mechanical, optical andbiological properties similar to pure acrylate IOLs. Unlike acrylicIOLs, silicone IOLs generally possess faster molecular response times.In fact, the silicone IOLs may be so responsive that when folded smallenough to be inserted through a 3 mm or smaller incision, the storedenergy can cause the IOL to unfold more quickly than desired.

In light of the above considerations, it may be desirable to configurean intraocular lens so that the haptics have mechanical properties thatdiffer from those of the optic to which they are attached. For examplethe optic may be fabricated from a material that has a relatively lowmodulus, while the haptics are made of another material having arelatively high modulus. However, not only can this two-materialapproach complicate supply requirements and the manufacturing process,there may also be incongruence between the two materials. The differencein materials may even result in a seam or even a weak physical linkbetween the optic and haptic portions of the IOL. In addition, if thehaptics protrude within an optic zone of the optic, the use of adifferent material having, for example, different refractive indices maylead to undesirable optical effects such as dysphotopsia or evenundesirable optical aberrations.

Accordingly, there is a need for a polymeric material with a molecularresponse time that makes it suitable for use near fragile body tissues.There is also a need for ophthalmic devices in which one polymericmaterial is useful for both low modulus and high modulus applicationsto, inter alia, simplify the multi-part polymeric article manufacturingprocess and create better integrated multi-part polymeric articles inwhich the various parts have a common value of a property such as arefractive index.

SUMMARY OF THE INVENTION

The subject matter herein solves the problems associated with previouspolymer materials by providing materials having moduli selectable byadjusting the amount of catalyst used to prepare the polymer.Alternatively or additionally, other mechanical properties of thematerial may be selected or adjusted. In some embodiments, the moduliselection may be affected by the hydride to vinyl ratio and/or theamount of cross-linking agent. Without wishing to be bound by theory, itis believed that methyl-vinyl cyclics (“MVCs”), which may be found inmany catalysts, especially platinum catalysts, contribute to thisphenomenon. In some embodiments, the impact on the modulus may be due tothe presence of an inhibitor or stabilizer in the catalyst that reducesthe hydride/vinyl ratio and/or prevent complete curing. In anotherembodiment, metals aside from platinum, more preferably transitionmetals, may be used. The siloxy materials discussed herein possessproperties that make them suitable for the manufacture, for example, ofboth optic and haptic portions of IOLs. In such embodiments, the hapticand optic comprise a common polymeric material that may have a commonvalue of a property, for example, having a common refractive index. Theresult is IOLs with a low modulus optic having a predeterminedrefractive index and, if prepared from the same components,well-integrated and resilient haptics. The IOLs will not damage theinserter cartridge or, more importantly, the surrounding ocular tissues.Low modulus polymers prepared as described herein also are idealstarting materials for many products implantable in patients (e.g.,IOLs, augmentation implants). A common refractive index, within at leastportions of both the optic and haptic portions, may advantageouslyreduce or eliminate glare, dysphotopsia, optical aberrations, and thelike, by reducing or eliminating refractive index gradients at theboundary between the optic and haptic portions. In some embodiments, theoptic of an ophthalmic device, such as of an IOL, has two or moreportions that may be fabricated such that the portions have a commonvalue of a property (e.g., a common material and/or a common refractiveindex), but have a different mechanical property, for example, adifferent moduli.

As an example, a siloxane component may be employed in the manufacturingof IOL materials. For example, the siloxane component may be a vinylterminated siloxane. The vinyl terminated siloxane may comprise motifsincluding, but not limited to, divinyl terminated siloxanes,methacrylate functional siloxanes, acrylate functional siloxanes andcombinations thereof. Preferably, the vinyl terminated siloxanes areselected from vinyl terminated diphenylsiloxane-dimethylsiloxanecopolymers, vinyl terminated polyphenylmethylsiloxanes,vinylphenylmethyl terminated vinylphenylsiloxane-phenylmethylsiloxanecopolymers, vinyl terminated polydimethylsiloxanes and combinationsthereof.

One embodiment is an intraocular lens having an optic and a haptic withdifferent moduli of elasticity and prepared from at least one commonunsaturated silicone fluid, a hydride crosslinking agent and a platinumcatalyst. In another embodiment, metals aside from platinum, morepreferably transition metals may be used. In another embodiment, theoptic and haptic also are prepared from at least one common hydridecrosslinking agent and/or at least one common platinum catalyst. In someembodiments, the optic and haptic have a common optical and/ormechanical property, for example, a common refractive index.

Another embodiment is a method for forming an intraocular lenscomprising an optic and a haptic and wherein said optic and said haptichave different moduli of elasticity but are prepared from at least onecommon unsaturated silicone fluid. The method may be practiced bycombining at minimum: an unsaturated silicone fluid, a hydridecrosslinking agent and a platinum catalyst to form the optic portion;combining the same unsaturated silicone fluid, a second hydridecrosslinking agent and a second platinum catalyst to form the hapticportion; and, joining the optic and haptic portions to form anintraocular lens. A skilled artisan knows several ways to join orco-form optic and haptic portions such that a unitary IOL is formed.

Another embodiment is a method for increasing the modulus of elasticityof a polymer by combining an unsaturated silicone monomer, a hydridecrosslinking agent and at least 0.1% by weight of a platinum catalystand/or at least one MVC. In order to increase the modulus of elasticity,the amount of platinum catalyst and/or MVCs may be increased. A skilledartisan will appreciate the ability to encompass control the modulus ofelasticity by varying the amount of platinum catalyst and/or MVCs usedto prepare a polymer.

Any of the previously discussed embodiments may be practiced inconjunction with the following embodiments related to the siliconefluid, catalyst, MVC, and/or H/V ratio. In one embodiment, the commonunsaturated silicone fluid may be a divinyl terminated silicone fluid,optionally having a pendant vinyl group. In another embodiment, thecommon unsaturated silicone fluid comprises monomers with the followingFormula 1, wherein the sum of m and n is x; x is at least about 1, morepreferably from about 5 to about 1200; y ranges from about 1 to about500; z ranges from about 0 to about 500; the sum of x, y, and z is atleast about 15; and R′ and R″ independently are optional pendant groupsthat may be selected from CH₃, C₆H₅, and CH═CH₂. In another embodiment,polymers can consist essentially of monomers depicted by Formula 1. Inother embodiments, polymers can consist of greater than 50% w/w ofmonomers having the structure of Formula 1, or greater than 75% w/w ofmonomers having the structure of Formula 1, or greater than 85% w/w ofmonomers having the structure of Formula 1, or greater than 90% w/w ofmonomers having the structure of Formula 1, or greater than 95% w/w ofmonomers having the structure of Formula 1.

In another embodiment, the unsaturated silicone fluid may comprisetetravinyltetramethylcyclotetrasiloxane,1,3-divinyltetramethyldisiloxane, or combinations thereof. In addition,the unsaturated silicone fluid also may include one or more ofoctamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, orcombinations thereof. In another embodiment, the hydride crosslinkingagent may be phenyltris(dimethylsiloxy)silane;tetrakis(dimethylsiloxy)silane; 1,1,3,3-tetraisopropyldisiloxane;1,1,3,3-tetramethyldisiloxane; 1,1,4,4-tetramethyldisilethanebis(dimethylsilyl)ethane; 1,1,3,3-tetramethyldisilazane; hydrideterminated polyphenyl-(di-methylhydrosiloxy)siloxane; or combinationsthereof. In another embodiment, the hydride crosslinking agent isphenyltris(dimethylsiloxy)silane.

In another embodiment, the platinum catalyst may be platinum carbonylcyclovinylmethylsiloxane complex, platinum-cyclovinylmethylsiloxanecomplex, platinum octanaldehyde complex, platinum octaoctanol compex, orcombinations thereof. In another embodiment, the platinum catalyst maybe present in an amount from about 0.1% to about 0.5% by weight.

In another embodiment, the MVC may be any methylvinyl siloxane, whichincludes cyclosiloxane and non-cyclosiloxane classes of materials.Nonlimiting examples of methylvinyl cyclosiloxane classes includetetramethylvinylcyclotetrasiloxane andpentamethylvinylcyclopentasiloxane. Non-cyclosiloxane classes include1,3-tetramethyldisiloxane, divinyltetraphenyldisiloxane,1,5-divinylhexamethyltrisiloxane, and1,5-divinyl-3,3-diphenyltetramethyltrisiloxane. One example of an MVC is1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane. In anotherembodiment, the MVC may be present in an amount of at least about 0.01%or at most about 1% by weight. It should be understood that for allpolymer embodiments described in the present application, MVC maypartially or completely substitute the catalyst, augment the catalyst orbe used to alter the H/V ratio. MVC is believed to have an inverselyproportional impact on the moduli of polymers prepared therewith.

In another embodiment, the unsaturated silicone monomer, said hydridecrosslinking agent, said platinum catalyst, and/or said MVC form across-linked polymer having a H/V ratio of about 0.6 to about 1.1.

Definitions of Terms

The terms and phrases used herein shall have the following,non-limiting, definitions.

Elongation: As used herein, “elongation” refers to the act oflengthening or stretching a polymeric material.

Full Elongation: As used herein, “full elongation” refers to the act oflengthening or stretching a polymeric material or polymeric IOL to itselastic limit.

Intermediate Elongation: As used herein, “intermediate elongation”refers to the act of lengthening or stretching a polymeric material orpolymeric IOL to a point between its original length and limit.

Glass Transition Temperature (T_(g)): As used herein, the “glasstransition temperature (T_(g))” refers to the temperature wherein apolymeric material becomes less elastic and more brittle. For softpolymeric materials described herein, T_(g) typically is not measuredsince it may be as low as −100° C. or lower.

Mass percent: As used herein, “mass percent” and “mass %” refer to themass of monomer present in a polymer divided by the total weight of thepolymer multiplied by 100. Mathematically, mass percent is representedby the following formula where M_(m) is the mass of the monomer andM_(P) is the mass of the corresponding polymer: [M_(m)/M_(p)]×100=MassPercent.

Compression Modulus or Modulus of Elasticity: As used herein “modulus ofelasticity” refers to the ratio of stress to strain. As used herein,“compression modulus” refers to the ratio of compressive stress tocompressive strain.

Moduli: As used herein, “moduli” refers to the plural form of modulus ormodulus of elasticity.

Percent Elongation: As used herein, “percent elongation” refers to thelength of an elongated polymer divided by the length of the originalpolymer. Mathematically, the percent elongation is represented by thefollowing formula where L is the length of the elongated polymer and L₀is the length of the corresponding non-elongated polymer:[L/L₀]×100=Percent Elongation.

Pliable: As used herein, “pliable” refers to the flexible nature of apolymeric material and to the flexibility of polymeric IOLs that can befolded, rolled or otherwise deformed sufficiently to be inserted througha 2 mm or less surgical incision.

kPa: As used herein, “kPa” refers to kilopascal, which is a unit ofpressure or stress and is the equal to 1000×Newton per meter squared(N/m²).

Resiliency: As used herein, “resiliency” refers to a polymericmaterial's or a polymeric IOL's inherent ability to return to itsunstressed configuration following impact, deformation in an inserter,or the resulting deformation associated with the stress on impact, alsoreferred to herein after as “rebound resiliency.”

Refractive Index (RI): As used herein, “refractive index (RI)” refers toa measurement of the refraction of light of a material or object, suchas an IOL. More specifically, it is a measurement of the ratio of thespeed of light in a vacuum or reference medium to the speed of light inthe medium under examination. The refractive index of a material orobject typically varies with the wavelength of the light, a phenomenonsometimes referred to as dispersion.

Common Refractive Index: As used herein, “common refractive index” shallrefer to the similarity of refractive indices between two materials. Acommon refractive index between two materials would be two materialswith a difference in refractive index at a particular wavelength of lessthan or equal to 5%, or less than or equal to 2%, or less than or equalto 1%, or less than or equal to 0.2%.

Softness: As used herein, “softness” refers to a polymeric material's ora polymeric IOL's pliability as opposed to, for example, apolymethylmethacrylate (PMMA) IOL that is rigid and hard.

Ultimate Tensile Strength: As used herein, “ultimate tensile strength”refers to the maximum stress a material can withstand before fractureand is measured in psi (lb/in²).

Clear Aperture: As used herein, “clear aperture” refers to the portionof an optic that limits the extent of the rays from an object thatcontributes to the conjugate image and is generally expressed as adiameter of a circle.

Common Polymeric Material: As used herein, “common polymeric material”refers to similarity of material composition between two objects orportions of an object. Two objects or portions of an object comprise acommon polymeric material if the two objects or portions consistessentially of the same base polymer chain or have at least 50% w/w ofthe same base polymer chain, or 75% w/w of the same base polymer chain,or 85% wlw of the same base polymer chain, or 90% w/w of the same basepolymer chain, or 95% wlw of the same base polymer chain, and, whenpresent, the same cross-linking agent.

DETAILED DESCRIPTION OF THE INVENTION

Polymer compositions with moduli or other mechanical properties that maybe altered based, for example, on the amount of catalyst, cross-linkingagent and/or MVC content are described herein. Also, low modulusmaterials produced as described herein exhibit mechanical qualities thatmake them excellent for implantation in living organisms, particularlyanimals, more particularly humans. Potential uses of the low modulusmaterials include, but are not limited to, IOL optics, breast or otheraugmentative implants, and controlled release devices (e.g.,pharmaceutical formulations). The mechanical qualities and feel of thelow modulus material make it possible to prepare bodily augmentationdevices that are implantable in a living organism, for example, breastimplants containing little or no liquid.

As for IOLs, it is desirable they can be folded, rolled or otherwisedeformed such that they can be inserted through small incisions.Furthermore, in order to reduce patient trauma and post surgicalrecovery time, the IOL preferably comprises a responsive polymer thatunfolds in a controlled manner. To meet these requirements, the polymerspreferably have minimal self tack and do not retain excessive amounts ofstored mechanical energy. However, if the IOL is too thin, or thepolymer lacks sufficient mechanical strength, it may be too fragile andeasily dislocated or damaged during or after the insertion process.

Historically, foldable IOL materials have been designed to be tough(tensile strength of greater than 750 pounds per square inch [psi]) andwith a relatively high percent elongation (greater than 100%). Theseproperties give the IOL sufficient toughness such that the IOL does nottear from the forces experienced during insertion through a 2.6 to 3.2mm incision. Presently available foldable IOLs include, among others,Sensar® (Advanced Medical Optics, Santa Ana Calif.), an acrylic IOLhaving a tensile strength of about 850 psi and an elongation at break ofabout 140%; SLM-2® (Advanced Medical Optics, Santa Ana Calif.), asilicone IOL having a tensile strength of about 800 psi and anelongation at break of about 230%; and AcrySof® (Alcon Laboratories,Fort Worth, Tex.) having a tensile strength of about 1050 psi. All threeIOLs are suitable for insertion through incision sizes of about 2.6 mmor greater. The polymers described herein are soft to very soft and maybe foldable.

Flexibility in monomer selection, which provides for control over thematerial's mechanical, optical and/or thermal properties are providedherein. For example, the ability to adjust a material's refractive index(RI) and mechanical properties is important in designing ultra-smallincision IOLs. Also, hydrophobic siloxy materials have demonstratedexcellent ocular biocompatibility. Thus, it surprisingly has beendiscovered that by utilizing the silicone materials in the preparationof IOL materials, an IOL optic can be made that has propertiespermitting its passage through an ultra small incision without damage tothe IOL, the inserter cartridge, or the eye. In addition, the IOL mayhave at least one resilient haptic that shares a common siloxy monomerwith the optic.

Silicones have unique properties derived from the inherent flexibilityof the siloxane bond. The alternating silicon-oxygen polymer backbone ofsiloxanes makes them remarkably more flexible than their organiccounterparts that have a carbon-oxygen backbone. This property ofsiloxanes results in low glass-transition temperatures (T_(g)) andexcellent flexibility. Furthermore, a low initial modulus is anotherimportant attribute of the novel siloxanes. In order to pass through theinsertion cartridge, a conventional refractive IOL must be capable ofelongating up to about 100%. Therefore, it is important that the initialmodulus be at optimum levels. A low initial modulus translates to lowstimulus required to express the IOL through the cartridge. Further,when the appropriate amounts of selected siloxanes, cross linkers andcatalysts are combined, the resulting material has the flexibility andmodulus required to make, for example, the optic portion of an IOLsuitable for insertion through a small incision without harming the IOL,the inserter cartridge or the eye.

In some embodiments, an intraocular lens comprises an optic and a hapticmade from a common polymeric material so that they also have a commonrefractive index; however, the optic and haptic have mechanical propertythat is different for each. In some embodiments, the IOL may be formedaccording to an embodiment so that the optic and haptic have differentmoduli of elasticity. For example, an accommodating IOL may be formed sothat the optic has a lower modulus than the haptic, thus allowing therelatively stiff haptic to protrude inside the relatively soft opticwithout causing unwanted reflections due to a refractive index mismatchat interfaces between the optic and the protruding haptic. Examples ofaccommodating IOLs having a stiffer protruding haptic are disclosed inco-pending U.S. patent application Ser. Nos. 11/618,411 and 11/618,325,which are herein incorporated by reference in their entirety. Thedifference in moduli between the haptic and optic may be provided by anadjustment in the amount of cross-linker and/or catalyst and/or MVCcontent of each IOL component. Embodiments herein may be used to provideIOL's in which at least the optic thereof has a modulus that is lessthan about 100 kPa, less than 75 kPa, or even less than 50 kPa or 25kPa. The stiffness of the haptic may be greater than 500 kPa, or greaterthan 3000 kPa, depending on the particular design requirements. In someembodiments, the modulus of the haptic is greater than that of the opticby at least 50%, by at least 150%, by at least 250%, or by at least500%. In some embodiments, the modulus may vary continuously over atleast some interface regions between the haptic and the optic, forexample, to provide a particular performance or stress distribution overthe IOL in reaction to an external force on the IOL (e.g., an ocularforce produced by the capsular bag, zonules, or ciliary muscle of an eyeinto which the IOL is inserted).

In some embodiments, an ophthalmic lens, such as an intraocular lens,comprises an optic having a clear aperture that comprises an innerportion and an outer portion disposed about said inner portion. Theinner portion and outer portion comprise a common polymeric material andmay have a common refraction index; however, the inner portion has amodulus that is different from that of the outer portion. The differencein modulus may be selected, for example, to control the amount and/orform of deformation of the optic in reaction to an external force suchas an ocular force produced by the capsular bag, the zonules, and/or theciliary muscle of an eye into which the optic is placed. In someembodiments, the refractive index may also vary between the zones, forexample, to control aberrations of the optic in a stressed or unstressedstate.

The modulus of the inner portion of the optic may by greater than orless than that of the outer portion, depending of the particular designrequirements. In some embodiments, the optic comprises three or morezones disposed within the clear aperture of the optic. In otherembodiments, the modulus of at least portions of the optic may varycontinually, for example, by producing a catalyst gradient throughout apolymeric fluid used to form the optic. In some embodiments, the zonesof the optic may have an ellipsoid or similar shape, such that themodulus varies from the center of the optic outward in athree-dimensional manner. Alternatively or additionally, the variationin modulus of the zones may vary in a two dimensional manner, forexample, forming concentric rings as the modulus varies in radialdirection from the optical axis of the optic. The difference in modulusbetween two zones of the optic may be greater than or equal to 5%, orgreater than or equal to 15%, or greater than or equal to 25%, orgreater than or equal to 50%, depending on the number of zones and thedesired performance of the optic under a given loading force.

The materials described herein may have low initial moduli and a lowglass transition temperature (T_(g)). Moreover, the IOLs may bemultifocal (i.e. refractive or diffractive), accommodating (i.e.deformable or movable under the normal muscle movements of the humaneye), highly biocompatible and have RIs ranging from about 1.40 to about1.56, preferably from about 1.41 to about 1.49, for light in the visiblewavelengths. These and other objects described herein may be achieved byproviding an unsaturated terminated silicone fluid and cross-linking itusing a hydride cross-linking agent and platinum catalyst. In anotherembodiment, transition metals aside from platinum, more preferablytransition such as, but not limited to, rhodium and palladium, may beused. Silicone fluids that may be cross-linked to prepare polymers withdifferent moduli simply by varying the amount of cross-linking agentand/or catalyst and/or MVC content are disclosed.

The unsaturated terminated siloxanes are preferably vinyl terminatedsiloxanes, more preferably multi-vinyl terminated. Non-limiting examplesinclude vinyl terminated diphenylsiloxane-dimethylsiloxane copolymers,vinyl terminated polyphenylmethylsiloxanes, vinyl terminatedphenylmethylsiloxane-diphenyldimethylsiloxane copolymers, vinylterminated polydimethylsiloxanes and methacrylate, and acrylatefunctional siloxanes. Other suitable silicone materials are disclosed inU.S. Pat. No. 6,361,561, the entirety of which is incorporated herein byreference. Representative materials can be obtained from Gelest, Inc.(Morrisville, Pa.) or synthesized using methods known to those skilledin the art.

In one embodiment, the unsaturated terminated siloxane is a vinylterminated siloxane comprising monomers comprising the structuredepicted in Formula 1 below. The polymers described herein can consistessentially of monomers comprising the structure of Formula 1. In otherembodiments, polymers can consist of greater than 50% w/w of monomershaving the structure of Formula 1, or greater than 75% w/w of monomershaving the structure of Formula 1, or greater than 85% w/w of monomershaving the structure of Formula 1, or greater than 90% w/w of monomershaving the structure of Formula 1, or greater than 95% w/w of monomershaving the structure of Formula 1. The values for x, y, and z in Formula1 will vary depending on, for example, the desired RI of the lens; and,in Formula 1, x is equal to the sum of m and n and is preferably atleast about 1. Preferably, IOLs described herein have an RI of at least1.40, more preferably at least 1.43. For example, if an IOL having arefractive index (“RI”) of 1.43 is desired, the x:y:z ratio may beapproximately 30:1:1; a x:y:z ratio of about 12:1:2 will result in anIOL having a RI of approximately 1.46. Skilled artisans can prepare anIOL having a desired RI, optical clarity and mechanical properties byadjusting the x:y:z ratio using skills known in the art and withoutundue experimentation. In one embodiment, x ranges from about 10 toabout 1200, y ranges from about 1 to about 500, z ranges from 0 to about500, and the sum of x, y, and z is from about 100 to about 1500. Inanother embodiment, x+y+z has a minimum value of about 200 in order toprovide a high softness polymer (e.g., when required for optic portionsof an IOL). R′ and R″ are optional pendant groups independently selectedfrom CH₃, C₆H₅, and CH═CH₂.

When z is equal to zero, the values for x and y still will varydepending on, for example, the desired RI of the lens and theunsaturated terminated siloxane will comprise monomers with thestructure depicted in Formula 2 below (also referred to as “AMO siliconefluid). In one embodiment, polymers can consist essentially of monomerswith the structure of Formula 2. In other embodiments, polymers canconsist of greater than 50% w/w of monomers having the structure ofFormula 2, or greater than 75% w/w of monomers having the structure ofFormula 2, or greater than 85% w/w of monomers having the structure ofFormula 2, or greater than 90% w/w of monomers having the structure ofFormula 2, or greater than 95% w/w of monomers having the structure ofFormula 2. For an IOL with a RI of 1.43, the x:y ratio may beapproximately 18:1; a x:y ratio of 5:1 will result in an IOL having a RIof approximately 1.46. Skilled artisans can prepare an IOL having adesired RI, optical clarity and mechanical properties by adjusting thex:y ratio using skills known in the art and without undueexperimentation. In one embodiment, x is at least 1, more preferablyfrom about 5 to about 10, y ranges from about 3 to about 8, and the sumof x and y is about 15. In another embodiment, x+y will have a minimumvalue of 400 for applications that require high softness. R′ and R″ areoptional pendant groups independently selected from CH₃, C₆H₅, andCH═CH₂.

Optionally, a number of ultraviolet (UV) and blue light absorbing dyescan be added to the silicone polymers described herein. For example, thesilicone IOLs may include 0.1 to 1.5 mass % of UV and blue lightabsorbing compounds such as benzophenone and benzotriazole-based UVlight absorbers or blue light blocking dyes including azo and methineyellow, which selectively absorb UV/blue light radiation up to about 450X. See, for example, U.S. Pat. Nos. 5,374,663; 5,528,322; 5,543,504;5,662,707; 6,277,940; 6,310,215 and 6,326,448, the entire contents ofwhich are incorporated herein by reference.

A variety of initiators for polymerization reactions are employedherein. In one non-limiting embodiment, peroxide initiators are used.Examples of peroxide initiators include, without limitation, about 0.100to about 1.50 mass % of di-tert-butyl peroxide (Trigonox® a registeredtrademark of Akzo Chemie Nederland B. V. Corporation Amersfoort,Netherlands) or 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane. Itshould be noted that peroxide initiators initiate the cross-linking ofvinyl groups on monomers (e.g., those on divinyl-terminated siliconemonomers). While this can help facilitate the cross-linking of thesilicone monomers, at least some of the hydride groups must still becross-linked as described herein.

One or more monomers may be cross-linked utilizing one or morehydride-containing cross-linkers such as, but not limited to:nonpolymetric X-linkers such as phenyltris(dimethylsiloxy)silane(Formula 3 below), tetrakis(dimethylsiloxy)silane (Formula 4 below),1,1,3,3-tetraisopropyldisiloxane, 1,1,3,3-tetramethyldisiloxane,1,1,4,4-tetramethyldisilethane bis(dimethylsilyl)ethane,1,1,3,3-tetramethyldisilazane; hydride terminated polymeric X-linkerswith different molecular weights such as DMS-H03, DHS-H11 to DMS-H41,hydride terminated polyphenyl-(di-methylhydrosiloxy)siloxane (HDP-111,Formula 5 below, wherein W is about 5 to about 50); HPM-502, which arecommercially available from Gelest; nonhydride terminated polymericcross-linkers such as XL-103, XL-110, XL-111, XL-112, XL-115, which arecommercially available from Nusil; and HMS-013, HMS-031, HMS-082,HMS-301, HMS-991, which are commercially available from Gelest. Othercross-linkers such as hydride Q resins may also be used to improve themechanical properties of the gels. The softness of the final gelformulations depends on the relative amount of cross-linker to vinylsilicone fluid (i.e. H/V [hydride-vinyl] ratio).

Properties of the silicone materials such as modulus, percent weightloss may be changed by varying the ratio of hydride and vinyl contents(H/V ratio) in the silicone fluids. Vinyl content of a silicone fluidmay be determined by, for example, the GPC method, titration, or NMR(nuclear magnetic resonance spectroscopy). By varying the ratio ofhydride primarily from the cross-linker and vinyl primarily from thevinyl silicone fluid, silicone materials with different moduli may beobtained. In certain embodiments, it is preferable for the H/V ratio tobe at least about 0.1, more preferably at least about 0.5, morepreferably about 0.6, more preferably about 0.7, more preferably about0.8, more preferably about 0.9, more preferably about 1.0, morepreferably about 1.1, more preferably about 1.25, and more preferably atmost about 1.5.

It was also surprisingly discovered herein that the modulus of materialis affected by the amount of catalyst and/or methyl-vinyl cyclics(“MVCs”) as well. Specifically, as the amount of catalyst and/or MVCs isincreased, the modulus of the material also increases until a peakmodulus is reached. After the peak modulus is reached, the modulusbegins to level off or, in many cases, decrease. FIG. 1 depicts therelationship between post-extraction modulus and % catalyst used forthree H/V ratios: 0.7, 1.125 and 1.55. As FIG. 1 shows, the point atwhich the modulus begins to level off or decrease depends not only onthe amount of catalyst or MVCs, but also on the monomers andcross-linking agents (which may impact H/V ratio) used to prepare thepolymer.

In general, platinum-containing catalysts work well. Exemplary platinumcatalyst include platinum-tetravinyltetramethylcyclotetrasiloxanecomplex, platinum carbonyl cyclovinylmethylsiloxane complex, platinumcyclovinylmethylsiloxane complex, platinum octanaldehyde/octanolcomplex. Many different platinum catalysts may be used depending on,inter alia, the desired pot life. Preferably, the platinum catalyst isused in amounts by weight of at least about 0.01%, more preferably atleast about 0.05%, even more preferably at least about 0,1%. Preferably,the platinum catalyst is used in amounts of about 1% or less, morepreferably about 0.75% or less, even more preferably about 0.5% or less,even more preferably about 0.4%, even more preferably about 0.3%, evenmore preferably about 0.2%.

In addition to platinum catalysis, other metal catalysis can be used. Insome embodiments, transition metals can be used as catalysts, morespecifically, palladium and rhodium catalysts can be used. Complexes andsalts of metal catalysts can be used. An example of a transition metalcomplex used as a catalyst is tris(dibutylsulfide)rhodium trichloride.

Without wishing to be bound by theory, one reason for the impact of somecatalysts, especially platinum catalysts, on the modulus may be due tothe presence of an inhibitor or stabilizer that may reduce thehydride/vinyl ratio and/or prevent complete curing. An example of suchan agent is a MVC such as cyclovinylmethylsiloxane (e.g.,1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane). It isworthwhile to note that the effects of catalyst amounts on modulus wereindependent of curing time. While MVCs sometimes are used as stabilizersin catalysts to, for example, prevent keep platinum suspended insolution, the MVCs typically are present in such small amounts that theyare inert.

This aspect unexpectedly was discovered when the platinum catalyst levelfor a polymer was increased to levels significantly higher thanconventionally used (e.g., up to 50 ppm versus a more traditional 10 ppmor less). A skilled artisan would expect that as catalyst concentrationincreases, curing time decreases and polymer cross linking increases.The skilled artisan also would expect this to lead to a more rigid orfirm polymer (even assuming curing temperature is the same). When thecatalyst was increased to atypical levels, a significant decrease incuring time was observed.

Contrarily, however, the resulting polymer was far less rigid and lessfirm than expected. Without wishing to be bound by theory, it isbelieved that when excessive amounts of catalyst were used, thecorresponding increase in MVCs allowed them to become reactiveingredients and end-cap the hydrides on the cross-linkers, whichresulted in more free ends on the structural polymers. The additionalfree ends provide a less-cross-linked and, therefore, less rigidpolymer. As a skilled artisan would appreciate, such a polymer is idealfor preparing many products including, but not limited to, productsimplantable in patients (e.g., IOLs, augmentation implants).

Herein, the MVC may be present in an amount of at least about 0.01%,about 0.05%, about 0.1%, about 0.11%, about 0.15%, about 0.2%, or about0.25% by weight; to at most about 1%, about 0.75%, about 0.5%, about0.4%, about 0.39%, about 0.35%, or about 0.35% by weight. It should beunderstood that for all polymer embodiments described herein, the MVCmay partially substitute the catalyst in any proportion or amountincluding completely or the MVC may augment the catalyst. The MVC isbelieved to have an inversely proportional impact on the moduli ofpolymers prepared therewith. It will be appreciated that all embodimentsdescribed herein, including IOLs and methods for producing them, mayincorporate the teachings regarding MVCs and their relationship to themoduli of polymer articles prepared therefrom.

When used for IOL optic portions, a polymer with a low initial modulus,as described herein, facilitates a more easily inserted IOL by reducingthe force required to express the polymer IOL through an insertercartridge. In addition, since the same starting materials may be usedfor both optic and haptic portions (only varying the H/V ratio and/or %catalyst or MVC), the material supply and manufacture of IOLs issimplified. An added benefit of using the same starting materials isthat the resulting optic and haptic portions will be more compatiblethereby facilitating more robust and/or seamless fusion.

EXAMPLE 1 Preparation of Polymer Discs

In one method for making a polymer, 129.43 grams ofoctaphenylcyclotetrasiloxane was placed in a preheated 1000 mL reactionkettle at 105° C. (+/−10° C.). The mechanical stirrer was turned on andthe whole system purged with nitrogen for at least 30 minutes. Next,666.16 grams of octamethylcyclotetrasiloxane and 4.50 grams of 1.3divinyl tetramethyl disiloxane were added to the reaction kettle. Then,3.14 grams of tetramethylammoniun siloxanolate was added to the reactionkettle. Stirring continued for at least 18 hours at 105° C. (+/−10C).The temperature of the kettle was then raised to 150° C. (+/−20C) for atleast 5 hours. After cooling, a clear silicone fluid was filteredthrough a 0.2 micron filter.

A Pope 2″ Wiped-Film stills unit was used to remove the volatilecomponents of the above silicone fluid by setting the chillertemperature to 5° C., still body temperature to 160° C., the vacuumrange to 0.8-2.2 torr and the rotor speed to 70 RPM. A total of 11.68%of the volatile components were removed at three different locations.GPC scans before and after wiped-film process showed the effectivenessof this step to remove volatile components. The efficacy of thewiped-film process was clearly demonstrated by the GPC scans as shown inFIG. 2. Most of the low molecular weight species were removed by thisprocess. Depending on the application, this process may be important forperformance since it significantly reduces the amount of leachablespecies in the resulting polymer product.

Next, 0.125 grams of2-(3′-t-butyl-2′-hydroxy-5′-vinyl-phenyl)-5-chlorobenzotriazole (UVAM)was added to 50 grams of the above silicone fluid. After centrifugalmixing, the fluid was placed in the 60° C. oven for 2 to 3 days untilthe UVAM was completely dissolved in the silicone fluid to make a “0.25%UVAM silicone fluid”. Varying amounts of a catalyst, in this caseplatinum-tetravinyltetramethylcyclotetrasiloxane complex, were added to20 grams of the 0.25% UVAM silicone fluid and centrifugally mixed toform “Part A” of the silicone fluid. The final catalyst concentration ofthree otherwise identical silicone fluids was, by weight, 0.1%, 0.3% and0.5%. “Part B” of the silicone fluid was prepared by mixing 0.0681 gramsof phenyltris(dimethylsiloxy)silane with 5 grams of the 0.25% UVAMsilicone fluid.

Next, 5 grams each of Part A and Part B were poured into a Teflon moldand cured in a 140° C. oven for 10 minutes to prepare “discs”. Aftersoxhlet extraction, some of the discs were placed in a fume hoodovernight and then placed in a 60° C. oven for 2 days before modulustesting. The modulus of these pre- and post-extraction discs wasmeasured using a Q8OO DMA (TA Instruments). After loading a sample onthe holder, the temperature was raised to 35° C. and allowed toequilibrate for 5 minutes before testing. Ramp force was applied to thedisc at 1 Newton/min to a maximum of 9 Newton. Modulus may be determinedby calculating the slope of two points from the resulting curve.

To demonstrate the impact of catalyst concentration on the modulus of apolymer at a fixed H/V ratio of 0.7, the three polymers with 0.1%, 0.3%and 0.5% by weight catalyst were tested. For each catalystconcentration, some discs underwent static IPA extraction (soxhlet) forone day and were dried in a vacuum oven for two days before modulusmeasurement. Curing conditions were also varied. The results, which aresummarized in Table 1, show that a polymer's modulus is sensitive to theamount of catalyst used to prepare the polymer. In this case, as theamount of catalyst was increased, the modulus of the material wasreduced. Discs with 0.5% catalyst were very soft and had a tendency todelaminate, therefore, no accurate modulus measurement could beobtained.

TABLE 1 Modulus of silicone samples at different catalyst levels andcuring history 0.1% catalyst 0.3% catalyst Modulus, KPa Modulus, KPaCuring Before After static Before After static 0.5% catalyst Conditionsextraction extraction extraction extraction Modulus, KPa 140° C., 10mins 155 157 54 53 Too soft 140° C., 10 mins 151 135 51 54 to test  60°C., 1 day 140° C., 10 mins 151 162 53 59  60° C., 3 days 140° C., 10mins 150 154 50 57  60° C., 5 days

EXAMPLE 2

A gel was prepared in accordance with Example 1; however, instead ofusing platinum tetravinyltetramethylcyclotetrasiloxane complex, 0.3%platinum carbonyl cyclovinylmethylsiloxane complex was used to preparethe silicone gel. The pot life of the silicone gel increased 1 hour(from 7 hours to 8 hours) without significantly changing the modulus ofthe final gel.

EXAMPLE 3

A divinyl terminated silicone fluid in accordance with Example 1;however, it was prepared using two different cross-linkers,phenyltris(dimethylsiloxy)silane (SIP) andtetrakis-(dimethylsiloxy)silane (SIT). The amount of cross-linker usedwas varied to prepare fluids with four different H/V ratios. Vinylcontent of the silicone fluids was determined by the GPC method. Aplatinum-cyclovinylmethylsiloxane complex was used to cure the polymers.Moduli of the sixteen polymers was measured both pre-extraction and poststatic extraction. It was found that by varying the amount ofcross-linker used in the vinyl fluid, silicone materials with differentmoduli could be obtained. It was also surprising to find that themodulus of the materials was also affected by the amount of catalyst.The curing time did not appear to be a factor in the modulus of thecured samples. The specifics of the experiment follow.

Divinyl silicone fluid (B36C) was mixed with two cross-linkers, SIP andSIT at four different (H/V) ratios and with 0.3% catalyst. In allsamples, enough UVAM(2-(3′-t-butyl-2′-hydroxy-5′-vinyl-phenyl)-5-chlorobenzotriazole) wasadded to the silicone fluids to provide a final concentration of 0.25%.Silicone discs were cured at 140° C. for 10 minutes. Some of the discsalso went through static IPA extraction for one day and were dried in avacuum oven for two days before modulus measurement. Moduli of thesesilicone samples before and after IPA extraction were determined using aQ800 DMA from TA instruments. Results of the compression modulus(average of 2 discs in each condition) and percentage weight loss aresummarized in the following two tables, Tables 2 and 3.

TABLE 2 Compression modulus of silicone samples at different H/V ratiosModulus with SIP Cross-Linker Modulus with SIT Cross-Linker (KPa) (KPa)H/V Before After Static Before After Static ratio Extraction ExtractionExtraction Extraction 1.5 104 196 496 631 1.0 588 669 544 635 0.7 64 7382 121 0.5 Too soft to test Too soft to test

TABLE 3 Percentage weight loss of silicone samples after 1 day staticIPA extraction H/V ratio SIP Cross-Linker (%) SIT Cross-Linker (%) 1.53.6 1.9 1.0 2.3 2.1 0.7 5.3 5.6

The vinyl terminated silicone fluids may have degrees of polymerizationof, for example, 200, 400, 600, 800, 1000 and 1200. The polymer ofExample 1 has a degree of polymerization of about 400 and a refractiveindex of about 1.43. An exemplary polymer with a degree ofpolymerization of about 600 comprises, by weight, about 86.69%octamethylcyclotetrasiloxane, about 12.92% octaphenylcyclotetrasiloxane,about 0.38% 1,3-divinyltetramethyldisiloxane, and 0.25%tetramethylammoniun siloxanolate. In addition, 0.25%2-(3′-t-butyl-2′-hydroxy-5′-vinyl-phenyl)-5-chlorobenzotriazolesubsequently may be added using the procedures of Example 1. Anexemplary polymer with a degree of polymerization of about 800comprises, by weight, about 86.78% octamethylcyclotetrasiloxane, about12.93% octaphenylcyclotetrasiloxane, about 0.29%1,3-divinyltetramethyldisiloxane, and 0.25% tetramethylammoniunsiloxanolate. In addition, 0.25%2-(3′-t-butyl-2′-hydroxy-5′-vinyl-phenyl)-5-chlorobenzotriazolesubsequently may be added using the procedures of Example 1.

EXAMPLE 4

In order to test the impact of MVCs on a polymer, a first polymercomposition was prepared with 0.1% catalyst while a second polymercomposition was prepared with 0.1% catalyst and 0,4% MVC (equivalent toabout 0.5% catalyst). Aside from catalyst/MVC content, the polymercompositions were otherwise identical. Also, six samples of each polymercomposition were cured at three different curing conditions (i.e., 2samples of each polymer at each curing condition). Two samples of thefirst polymer and two samples of the second polymer were cured at 140°C. for 10 minutes. Two samples of each polymer composition also werecured at 140° C. for 3 hours. And, two samples of each polymercomposition also were cured at 140° C. for 10 minutes followed by curingat 60° C. for 5 days. The average modulus for the first polymercomposition was in the range of about 132 to about 195 KPa, which issimilar to the 0.1% catalyst-containing polymer results shown inTable 1. None of the samples of the second polymer composition preparedwith 0.1% catalyst and 0.4% MVC could be removed from the curing traysfor modulus measurement since they were too soft to test. As can beappreciated, increasing the amount of catalyst/MVC may increase thereactivity of different species and may thereby reduce the amount ofunreacted species. An exemplary MVC, e.g.1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane, may bepurchased from Gelest (SIT 7900.0) or United Chemical Technologies (UCTCatalog No. T2160).

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe specification and attached claims are approximations that may varydepending upon the desired properties sought to be obtained. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopedescribed herein are approximations, the numerical values set forth inthe specific examples are reported as precisely as possible. Anynumerical value, however, inherently contains certain errors necessarilyresulting from the standard deviation found in their respective testingmeasurements.

The terms “a,” “an,” “the” and similar referents used herein (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. Recitation of ranges of values hereinis merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range. Unlessotherwise indicated herein, each individual value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein is intended merely to better illuminate and do not posea limitation on the scope otherwise claimed. No language in thespecification should be construed as indicating that any non-claimedelement is essential to the embodiments disclosed herein.

Groupings of alternative elements or embodiments disclosed herein arenot to be construed as limitations. Each group member may be referred toand claimed individually or in any combination with other members of thegroup or other elements found herein. It is anticipated that one or moremembers of a group may be included in, or deleted from, a group forreasons of convenience and/or patentability. When any such inclusion ordeletion occurs, the specification is deemed to contain the group asmodified thus fulfilling the written description of all Markush groupsused in the appended claims.

Certain embodiments are described herein, including the best mode, ifknown to the inventors at the time of filing. Of course, variations onthese described embodiments will become apparent to those of ordinaryskill in the art upon reading the foregoing description. The inventorexpects skilled artisans to employ such variations as appropriate.Practice of modifications and equivalents of the subject matter recitedin the claims is expected. Moreover, any combination of theabove-described elements in all possible variations thereof isencompassed herein unless otherwise indicated or otherwise clearlycontradicted by context.

Furthermore, references have been made to patents and printedpublications throughout this specification. Each of the above-citedreferences and printed publications individually are incorporated hereinby reference in their entirety.

In closing, it is to be understood that the embodiments disclosed hereinare for illustrative purposes. Other modifications may be employed andare within the scope of the claims. Thus, by way of example, but not oflimitation, alternative configurations may be utilized in accordancewith the teachings herein. Accordingly, the teachings herein are notlimited to that precisely as shown and described.

1-11. (canceled)
 12. A method for forming an intraocular lens comprisingan optic and a haptic, the method comprising: combining an unsaturatedsilicone fluid, a hydride crosslinking agent and a platinum catalyst toform said optic; combining said unsaturated silicone fluid, a secondhydride crosslinking agent and a second platinum catalyst to form saidhaptic such that said optic and said haptic have a common refractiveindex and a different modulus of elasticity, and wherein the optic has amodulus of elasticity of less than about 100 Kpa, and, joining saidoptic and said haptic to form an intraocular lens.
 13. A method forforming an intraocular lens according to claim 12, wherein said hydridecrosslinking agent and said second hydride crosslinking agent are thesame.
 14. A method for forming an intraocular lens according to claim12, wherein said platinum catalyst and said second platinum catalyst arethe same.
 15. A method for forming an intraocular lens according toclaim 12, wherein said unsaturated silicone fluid comprises a divinylterminated silicone monomer.
 16. A method for forming an intraocularlens according to claim 12, wherein said unsaturated silicone fluidcomprises monomers having Formula 1:

wherein the sum of m and n is x, x ranges from about 1 to about 1200, yranges from about 1 to about 500, and z ranges from 0 to about 500, thesum of x, y, and z is at least about 15, and R′ and R″ are optionalpendant groups independently selected from CH₃, C₆H₅, and CH═CH₂.
 17. Amethod for forming an intraocular lens according to claim 12, whereinsaid common unsaturated silicone fluid comprises monomers selected fromoctamethylcyclotetrasiloxane, octaphenylcyclotetrasiloxane,tetravinyltetramethylcyclotetrasiloxane,1,3-divinyltetramethyldisiloxane, and combinations thereof.
 18. A methodfor forming an intraocular lens according to claim 12, wherein saidhydride crosslinking agent and said second hydride crosslinking agentindividually are selected from phenyltris(dimethylsiloxy)silane;tetrakis(dimethylsiloxy)silane; 1,1,3,3-tetraisopropyldisiloxane;1,1,3,3-tetramethyldisiloxane; 1,1,4,4-tetramethyldisilethanebis(dimethylsilyl)ethane; 1,1,3,3-tetramethyldisilazane; hydrideterminated polyphenyl-(di-methylhydrosiloxy)siloxane; and combinationsthereof.
 19. A method for forming an intraocular lens according to claim12, wherein said hydride crosslinking agent and said second hydridecrosslinking agent are phenyltris(dimethylsiloxy)silane.
 20. A methodfor forming an intraocular lens according to claim 12, wherein saidplatinum catalyst and said second platinum catalyst are individuallyselected from the group consisting of platinum carbonylcyclovinylmethylsiloxane complex, platinum-cyclovinylmethylsiloxanecomplex, platinum octanaldehyde complex, platinum octaoctanol compex;and combinations thereof.
 21. (canceled)
 22. (canceled)
 23. A method offabricating an article of manufacture having a first and a secondportion, comprising: a) combining a polymeric material and a firstconcentration of a catalyst to form said first portion; b) combiningsaid polymeric material and a second concentration of a catalyst to formsaid second portion; wherein said first portion and said second portionare co-formed or joined; wherein said first portion and said secondportion have a different modulus of elasticity; and wherein said firstportion and said second portion have about the same refractive index.24. The method of claim 23, wherein said article of manufacture is anintraocular lens, said first portion comprising an optic, and saidsecond portion comprising at least one haptic.
 25. The method of claim23, wherein said article of manufacture is an optic, said first portioncomprising an inner portion of said optic and the second portioncomprising an outer portion of said optic dispersed about said innerportion.